Mobec DOES make a 2-wheel-drive setup using the BMW paralever final drive,
but it comes out of the opposite side of the unit for sidecars mounted to the right (correct ) side of the bike...

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What you are showing looks like a home-grown setup, but nicely done.

Although I would use a splined shaft with a boot rather than a rigid welded shaft to allow for some change in length with suspension movement,
and also to allow the shaft to be moved out of the way more easily for wheel changes.
Unless it is splined where it goes into the CV joints???

I also prefer welded wheels (or cast) vs. multi-part bolted/riveted wheels.
- No joints to maintain an airtight seal on.
- No worries about the fasteners loosening up over time/stress.
- No worries of stress cracking/fractures at all the many small drilled holes.
- Easier to clean (fewer/no sharp corners for dirt/mud to get stuck in).
But again, that is just a personal preference...

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The idea of the locking hub is a good one. Mobec is a full-time 2WD, with no differential.
I have been playing around with some ideas/plans for a full-time 2WD sidecar rig based upon a BMW Boxer motorcycle, but chucking the entire stock swingarm and hanging the rear suspension for the bike and sidecar off of the sidecar frame; & using a racing cart limited-slip differential w/reverse built into it to tranfer power. I am still looking for a suitable donor bike for the project.

Be interesting to see what you come up with and at what costs using a freewheeling unlocking hub from a 4WD vehicle since all it does is didconnect the wheel from the axle. Probably be easier to use a system like the little XJ Cherokees w/D30 axle and earlier 83/84 full size Wagoneers w/D44 axle used. It was a vacuum actuated splined collar and a two piece front axle shaft where the collar slides over the inner axle shaft connecting the two pieces. On a bike you could use a lever to slide the collar instesd of a vacuum motor. Be cheaper to get the shaft cut and splined than the machining needed to make an unlocking hub work.

Be interesting to see what you come up with and at what costs using a freewheeling unlocking hub from a 4WD vehicle since all it does is didconnect the wheel from the axle. Probably be easier to use a system like the little XJ Cherokees w/D30 axle and earlier 83/84 full size Wagoneers w/D44 axle used. It was a vacuum actuated splined collar and a two piece front axle shaft where the collar slides over the inner axle shaft connecting the two pieces. On a bike you could use a lever to slide the collar instesd of a vacuum motor. Be cheaper to get the shaft cut and splined than the machining needed to make an unlocking hub work.

Before I got Temporarily sabotaged by working away from home so much and various things like the inlaws passing away. And thus side tracked some what. I bought a Subaru viscous coupler and various bits on eBay towards building a 2wd outfit. As I see it taking drive from a chain drive bike "should" be fairly simple. As in without building a cut down motor car. But will see when I get that roundtuit again. Meanwhile with baited breath.......